There is a demand for the tires of heavy-load vehicles (heavy-load tires) to have the properties of low heat build-up and wear resistance, in particular. Under such circumstances, rubber compositions containing a carbon black or a silica compounded with a rubber component containing a natural rubber as a main component are primarily used as rubber compositions for heavy-load tires.
For example, a rubber composition for a tire tread suitable for a heavy-load pneumatic tire containing a carbon black and a diene rubber containing not less than 50 mass % of a natural rubber is disclosed in Patent Document 1 (claims, paragraph [0031]).